EU-Rent car rentals specification

EU-Rent is a widely known case study being promoted as a basis for demonstration of product capabilities. However, no in-depth case analysis neither specification has been developed. Therefore, it was considered interesting, useful and even necessary to develop a complete study of the case, which would lead to its whole specification. On the other hand, it was considered a good opportunity to test the application of some proposals, such as alternate mechanisms to define integrity constraints and derivation rules, as well as an alternative approach to model events.Postprint (published version

CAPre: Code-Analysis based Prefetching for Persistent object stores

Data prefetching aims to improve access times to data storage systems by predicting data records that are likely to be accessed by subsequent requests and retrieving them into a memory cache before they are needed. In the case of Persistent Object Stores, previous approaches to prefetching have been based on predictions made through analysis of the store’s schema, which generates rigid predictions, or monitoring access patterns to the store while applications are executed, which introduces memory and/or computation overhead. In this paper, we present CAPre, a novel prefetching system for Persistent Object Stores based on static code analysis of object-oriented applications. CAPre generates the predictions at compile-time and does not introduce any overhead to the application execution. Moreover, CAPre is able to predict large amounts of objects that will be accessed in the near future, thus enabling the object store to perform parallel prefetching if the objects are distributed, in a much more aggressive way than in schema-based prediction algorithms. We integrate CAPre into a distributed Persistent Object Store and run a series of experiments that show that it can reduce the execution time of applications from 9% to over 50%, depending on the nature of the application and its persistent data model.This work has been supported by the European Union’s Horizon 2020 research and innovation program under the BigStorage European Training Network (ETN) (grant H2020-MSCA-ITN-2014- 642963), the Spanish Ministry of Science and Innovation (contract TIN2015-65316) and the Generalitat de Catalunya, Spain (contract 2014-SGR-1051).Peer ReviewedPostprint (author's final draft

An analysis pattern for electronic marketplaces

An electronic marketplace supports the interaction among different users to exchange information about products to sell and buy. Significance of electronic marketplaces is given by the huge amount of web sites that are currently available providing services in almost any area one can think of. However, existing similarities among these sites are not precisely documented which strongly restrains software reuse during the development of new electronic marketplaces. To improve this situation, we propose an analysis pattern that describes both the structural and the behavioural properties of a generic electronic marketplace. Then, developing a new electronic marketplace will correspond just to provide a particular adaptation of our pattern. In this way, reuse of our pattern contributes to reducing the costs of the development of new electronic marketplaces.Postprint (published version

Validation of UML conceptual schemas with operations

The purpose of validating a conceptual schema is to guarantee that it properly reflects what the user needs from an application. This task is not fully formalizable, so it is desirable to provide the designer with a set of tools that assist him or her in the validation process. A conceptual schema specifies the relevant information about the domain, and how this information changes as a result of operations. In this sense, we propose an approach to validate a UML conceptual schema by simulating the execution of the operations defined in it, so that the designer can check both that the schema is correctly defined and that it satisfies the requirements.Postprint (published version

Strict and extended interpretations of operation contracts in conceptual modeling

This paper describes two different ways of understanding operation contracts in conceptual modeling. The main difference between them lies in the way operation postconditions and integrity constraints are guaranteed, which impacts on the desirable properties of operation contracts according to recommended good practices for requirements specification. Both approaches are formalized and then compared in a number of issues.Postprint (published version

Machine Learning-based Query Augmentation for SPARQL Endpoints

Linked Data repositories have become a popular source of publicly-available data. Users accessing this data through SPARQL endpoints usually launch several restrictive yet similar consecutive queries, either to find the information they need through trial-and-error or to query related resources. However, instead of executing each individual query separately, query augmentation aims at modifying the incoming queries to retrieve more data that is potentially relevant to subsequent requests. In this paper, we propose a novel approach to query augmentation for SPARQL endpoints based on machine learning. Our approach separates the structure of the query from its contents and measures two types of similarity, which are then used to predict the structure and contents of the augmented query. We test the approach on the real-world query logs of the Spanish and English DBpedia and show that our approach yields high-accuracy prediction. We also show that, by caching the results of the predicted (More)This work has been supported by the European Union's Horizon 2020 research and innovation program (grant H2020-MSCA-ITN-2014-642963), the Spanish Ministry of Science and Innovation (contract TIN2015-65316, project RTC-2016-4952-7 and contract TIN2016-78011-C4-4-R), the Spanish Ministry of Education, Culture and Sports (contract CAS18/00333) and the Generalitat de Catalunya (contract 2014-SGR-1051). The authors would also like to thank Toni Cortes for his feedback.Peer ReviewedPostprint (author's final draft

OCL-Lite: a decidable (yet expressive) fragment of OCL

UML has become a de facto standard in conceptual modeling. Class diagrams in UML allow one to model the data in the domain of interest by specifying a set of graphical constraints. However, in most cases one needs to provide the class diagram with additional semantics to completely specify the domain, and this is where OCL comes into play. While reasoning over class diagrams is decidable and has been investigated intensively, it is well known that checking the correctness of OCL constraints is undecidable. Thus, we introduce OCL-Lite, a fragment of the full OCL language and prove that reasoning over UML class diagrams with OCL-Lite constraints is in ExpTime by an encoding in the description logic ALCI. As a side result, DL techniques and tools can be used to reason on UML class diagrams annotated with arbitrary OCL-Lite constraints.Peer ReviewedPostprint (published version

Towards DaaS 2.0: Enriching Data Models

Current Data as a Service solutions present a lack of flexibility in terms of allowing users to customize the underlying data models by including new concepts or functionalities. Data providers either publish global APIs to make data available, or 'sell' and transfer data to clients so they can do whatever they want with it. Thereby, collaboration and B2B becomes limited and sometimes is not even feasible. Our technology implements the necessary mechanisms for data providers to enable their clients to enrich data models both with additional concepts and with new methods that can be executed and, in turn, published as new services.Postprint (author’s final draft

Specifying artifact-centric business process models in UML: technical report

In recent years, the artifact-centric approach to process modeling has attracted a lot of attention. One of the research lines in this area is finding a suitable way to represent the dimensions in this approach. Bearing this in mind, this paper proposes a way to specify artifact-centric business process models by means of well-known UML diagrams, from a high-level of abstraction and with a technology-independent perspective. UML is a graphical language, widely used and with a precise semantics.Preprin

EU-Rent as an artifact-centric process model: technical report

Business process modeling using an artifact-centric approach has raised a significant interest over the last few years. This approach is usually stated in terms of the BALSA framework which defi nes the four dimensions of an artifact-centric business process model: Business Artifacts, Lifecycles, Services and Associations. One of the research challenges in this area is looking for diff erent diagrams to represent these dimensions. Bearing this in mind, this technical report shows how various UML diagrams can be used to represent all the elements in the BALSA framework by applying them to the EU-Rent case study.Preprin